Convergence means



0 F HAMANN CONVERGENCE MEANS Filed March 29, 1956 Oct. 7, 1958 INVENTOR.

OMER F. HAMANN.

ATTORNEY United States Patent O CONVERGENCE MEANS Omer F. Hamann, SanDiego, Calif., assignor to General Dynamics Corporation, Rochester, N.Y., a corporation of Delaware Application March 29, 1956, Serial No.574,726

2 Claims. (Cl. 313-77) This invention relates generally to acomponentfor utilization with a cathode ray tube, and more particularly,to an improved convergence means.

Convergence means are utilized in many cathode ray tube constructions toeffect various desired electromagnetic fields to influence or control anelectron beam generated by the cathode ray tube. One type of suchcathode ray tube utilizing convergence means is a cathode ray displaytube such as is shown and described in the copending application ofJoseph T. McNaney et al., Serial No. 507,856, now Patent No. 2,824,250,and my copending application Serial No. 507,902, both assigned to thecommon assignee hereof, wherein the convergence means is utilized toeffect desired focusing and imaging actions upon character shaped beams.In the prior art, it has been found necessary to provide a plurality ofmechanical controls to eifect a proper alignment of the convergencemeans about the neck of the cathode ray tube,

as is exemplified in Serial No. 507,856. Because of the inherentgeometry of the tube, the adjustments to the convergence means mustgenerally be made at or near the means itself and at some distance fromthe screen. The person adjusting the tube therefore generally does nothave a first-hand view of the screen and can only see the reflection ofthe display by means of mirrors to evaluate the images of the display.The convergence means includes a main convergence coil which is of anelectromagnetic type and designed with predetermined electro-opticalproperties. The convergence coil is designed to effect desired beamfocus, imaging and convergence of the electron beam according topredetermined conditions within the cathode ray tube. The coil,generally, is utilized in the display tubes not only to redirect thepath of the electron beam to a convergence or cross over point along theelectrooptical axis, but also to achieve predetermined imagingcharacteristics of the cross section of the beam upon the target. As istaught in my copending application Serial No. 507,902, proper imaging ofthe cross section of the electron beam necessitates predeterminedelectrical spacing relationships between the electrical center or axisof the convergence coil, the beam, and the electrical or electro-opticalaxis of the tube.

It has been found necessary to provide about 5 of motion to theconvergence coil to properly adjust it about the neck of a display tube,for example. It will there fore be seen that it is important, bothinitially and during operation of the display tube, to effectadjustments of the electrical axis of the convergence coil from time totime to maintain the required parameters. The mechanical adjustingneeded to effect adjustment of the convergence coil so that the axisthereof was generally coaxial with the electro-optical axis consisted ofmechanical adjustments to effect vertical translation, horizontaltranslation, pitch, yaw and translation along the electro-optical.

axis of the tube. One of the objects of this invention ICC is to reducethe mechanical adjustments to a single translation adjustment along theoptical axis of the tube and an adjustment to maintain the electricalaxis of the coil substantially coaxial with the electro-optical axis ofthe tube.

The present invention overcomes these disadvantages by eliminating thecomplex mechanical adjustments. The invention utilizes the convergencecoil as taught in my copending application Serial No. 507,902 as thebasic component. The coil is disposed adpacent and substantialysymmetrically with the cathode ray tube. About the convergence coil isdisposed a plurality of auxiliary windings which produce electromagneticdeflecting fields substantially orthogonal with the electrical axis ofthe coil. The deflecting windings are utilized to compensate formisalignment of the tube elements, to compensate for effects of straydirect current fields and to further compensate for small mechanicalmisadjustments of the convergence coil itself.

It is another object of this invention to provide a substantiallyelectrically alignable convergence means for cathode ray tubes.

It is another object of this invention to provide a new and improvedconvergence means which may be electrically adjusted from a remoteposition to effect its proper alignment.

It is another object of this invention to provide a new and improvedconvergence means which may be simply and easily mounted about the neckof a cathode ray tube.

It is another object of the present invention to provide a convergencemeans whose mount assembly is of reduced complexity and cost.

It is another object of this invention to provide a new and improvedconvergence means which permits utilization of shielding structure ofreduced complexity and cost.

It is another object of this invention to provide a new and improvedconvergence means whose alignment adjustments can be made with greatease by a substantially inexperienced operator.

Objects and advantages other than those set forth above will be apparentfrom the following description when read in connection with theaccompanying drawings, in which:

Figure 1 is a view of a portion of a cathode ray tube in perspectiveembodying the invention;

Figure 2 is a view in perspective of a convergence means, with cut-awaysections, embodying the invention;

Figure 3 is a view in cross-section along line IIIIII of Figure 2;

Figure 4 is a schematic representation of a circuitry which may be usedto effect the necessary alignment adjustments in the convergence means.

Figure 1 shows generally a portion of a cathode ray tube 10, which maybe of any known type, but is shown here as a cathode ray display tubesuch as is exemplified in the aforementioned copending applicationsSerial Nos. 507,856 and 507,902. At one end of the tube 10 is positioneda beam generating means 11 which provides and projects an electron beam12 generally along a predetermined electro-optical or electrical axis 13of the tube 10 for impingement upon a target 14, such as a fluorescentscreen. Intermediate the generating means 11 and target 14 is positioneda selection means 15, which may be of any known deflection plate or yokedesign, but is shown as a pair of vertical and a pair of horizontalelectrostatic deflection plates. The selection means 15 is used toposition the beam both horizontally and vertically to a desired portionof a matrix 18 whereby desired characters formed in the matrix areilluminated. The matrix 18 is positioned generally intermediate thetarget 14 andthe selection means 15.

Intermediate the matrix 18 and the target 14 and positioned about theneck of the tube 10 is a convergence means 19. The convergence means 19acts through its electromagnetic field to effect predetermined control,such as convergence and imaging, upon the electron beam 12 after thebeam leaves the matrix 18. A positioning means 20, located generallyintermediate the convergence means 19 and target 14 effectspredetermined positioning deflection upon the beam 12 to position thebeam crosssection on the target 14 at any desired position.

As is taught in my prior application, it is important to direct theelectron beam 12 along predetermined paths and further to effectpredetermined convergence, focusing and imaging actions upon the crosssection of the electron beam. To accomplish this result the electricalaxis of the convergence means and the electro-optical axis of the tube10 must be oriented to a substantially common axis along which theelectron beam may be projected. Proper alignment of the electron beamwith the convergence means has been found to require at least of angularmotion and some translatory motion of the convergence means whereby theconvergence means is properly adjusted about the neck of the tube toeffect the desired orientation. Such orientation of the convergencemeans effects control of the beam in vertical translation, horizontaltranslation, pitch, yaw and translation along the electrical orelectro-optical axis 13 of the tube 10.

The convergence means 19, shown in greater detail in Figures 2 and 3,includes two pair of deflection windings or coil units 22, 23, 24 and 25which are disposed adjacent and may be disposed generally about a mainconvergence coil 26. The coils may be formed in any known manner and areshown here as a wound coil,-

namely, main convergence coil 26 and four printed circuit coils 22, 23,24 and 25. However, it should be expressly understood that thedeflection coils 22, 23, 24 and 25 may also be of a wound coilconstruction rather than a printed circuit construction and still fallwithin the present invention. The deflection windings or coils 22, 23,24 and 25 are shown as preferably each of a semi-cylindrical shape anddisposed with another to form substantially a cylindrical shape. Coils22, 23, 24 and 25 are substantially symmetrically disposed about themain convergence coil 26, and act to set up horizontal and verticaldeflecting fields generally perpendicular to electrical axis 27 of themain coil 26. The deflecting fields set up by the windings 22, 23, 24and 25 may be utilized to effect vertical and horizontal translation,pitch and yaw, and a slight translation along the electro-optical axis13 of the tube 10.

Coils 22 and 23 are shown disposed about main coil 26 and disposed 180apart from each other with their concavities facing each other. Coil 22and 23 are connected together electrically as shown schematically inFigure 4. Coils 24 and 25 are rotated 90 from the position of coils 22,23 and are likewise disposed 180 apart from each other with theirconcavities facing each other and series connected. Therefore, coils 22and 23 and coils 24 and 25 are positioned in orthogonal relationship toone another to effect respectively vertical and horizontal deflectingfields which are substantially perpendicular to the field of the mainconvergence coil 26;

In addition, a pair of trim windings 30, 31, which may be of any knownconstruction but are shown here as coils of conductors, are used oneither end of the main convergence coil 26 to effect additional controlupon field generated by the main convergence coil 26.

It has been found by experimentation that the deflecting currentsnecessary in the coils 22, 23 and coils 24, 25 to effect desiredalignment of the electro-optical a s 13 and the electrical axis 27 ofthe main convergence coil 26 is a rather small current on the order of30 milliamperes. It is possible, therefore, by utilizing a circuitry,for example, as is shown in Figure 4, where a power supply 37 of knownconstruction, furnishes power to the circuit. A main potentiometer 38regulates the power to the circuit. A plurality of cross connectedpotentiometers 39 are utilized to permit adjustment in windings 22, 23and 24, 25 to effect the various desired vertical and horizontaltranslations, pitch and yaw and to provide slight translation along theelectro-optical axis 13 of the tube 10. Utilization of the instantinvention also increases the sharpness and clarity of the resultingdisplay upon the target 14 of the tube 10.

The convergence coil 26 carrying the deflection coils may be simplysymmetrically mounted about the neck of the tube 10, as shown in Figurel, by any known means of directly mounting the coil on the neck of thetube, but is shown in the preferred embodimentas being accomplished byclamping with clamps 33, 34 of aplastic insert 35 the coil 26 directlyto the neck of the tube 10. It is therefore possible as the coil 26 iscompletely independent of the tube shielding, to reduce the complexityof the shield necessary to effect shielding of the coil and to eliminatethe various complicated shield movements needed heretofor to adjust thecoil mechanically. Therefore, the various alignment adjustments of theelectron beam to compensate for tube element misalignments, straymagnetic fields and minor mechanical misadjustments of the convergencecoil may all be accomplished in a straight forward manner by a singleoperator at the tube screen by varying selectively potentiometers 38 and39. Further, considerable reduction in cost is effected by eliminationof the complex mechanical adjustments and suspensions. The improvementin the tube shielding likewise is of considerable advantage in that theshield need no longer be movable and may now be directly applied abovethe coil to shield against stray electromagnetic fields.

The particular embodiment of the invention illustrated and describedherein is illustrative only and the invention includes such othermodifications and equivalents as may readily appear to those skilled inthe art within the scope of the appended claims.

I claim:

1. In a cathode ray display tube construction wherein an electron beamis generated and projected along an axis toward a target, a beam shapingmember is disposed in the path of the beam to effect a desired crosssectional shaping upon the beam and an electromagnetic convergence meansis electromagnetically coupled with said beam, the improvements in saidconvergence means comprising a main convergence coil having anelectrical axis when energized, deflection windings substantiallyencircling said convergence coil for producing variable intensity fieldssubstantially orthogonal with said electrical axis when energized, saidfields being capable of displacing said electrical axis in response tothe intensity of said fields to cause coaxial alignment of said axiswith said electrical axis.

2. In a cathode ray display tube construction wherein an electron beamis generated and projected along an axis toward a target, a beam shapingmember is disposed in the path of the beam to effect a desired crosssectional shaping upon the beam and an electromagnetic convergence meansis electromagnetically coupled with said beam, the improvements in saidconvergence means comprising a main convergence coil having anelectrical axis when energized, four windings orthogonally disposedabout and adjacent said convergence coil, said coil and saidWindingvbeingsYmTfimaHyFW with respect to one another, said windingswhen energized having a field capable of adjustment to effectdisplacement of said electrical axis coaxial with said axis.

(References on following page) 6 References Cited in the file of thispatent 2,692,355 Sickles et a1. Oct. 19, 1954 2,719,249 Friend Sept. 28,1955 2151530 E E STATES PATENT; 21 1939 2,793,311 Thomas May 21, 1957 usa ar. 2,167,379 Tolson July 25, 1939 5 OTHER REFERENCES 2,414,925Buckbee Jan. 28, 1947 Martin: Printed Crossed-Field Deflecting Coils, Tele- 2,539,492 Smyth Jan. 30, 1951 Tech and Electronic Industries,December 1954, pages 2,653,262 Bowman Sept. 22, 1953 82, 83, 140 and141.

